1. Field of the Invention
This invention relates to a method for completing a wellbore with casing. More particularly, the invention involves a method for concurrently setting a lower uncemented casing and an upper cemented casing to allow rotation of only the upper casing while cementing.
2. Discussion of the Art
One of the most critical operations in completing a well to bring it into production is cementing the annulus between the casing and the wellbore. The cement must isolate different formations traversed by the wellbore to prevent formation fluids from moving along the annulus.
To achieve a quality cement job, the drilling mud in the annulus must be substantially displaced by cement and by preflushes which are pumped ahead of the cement. Field operations over the past two decades have demonstrated that rotating the casing during the mud displacement and cementing operation is beneficial. See, for example, the following articles: Hyatt, C. R., et al., "Liner Rotation and Proper Planning Improve Primary Cementing Success," SPE 12607 (1984); Arceneaux, M. A., "Liner Rotation While Cementing: An Operator's Experience in South Texas," SPE/IADC 13448 (1985); and Webster, M. B. et al., "Cementing High-Angle Wells Using Cement-Expanded Formation Packers and/or Casing Rotation," SPE/IADC 16136 (1987).
Although casing movement is desirable, rotation of the entire casing string during cementing has been impractical or impossible in some situations. For example, the torque required to rotate casing in deep wells or in highly deviated or horizontal wells can exceed the torsional limits of the casing or the casing threaded connections. Without casing rotation, a poor cement job can result and necessitate cement squeeze jobs or workovers.
Another alternative has been to cement a first section of casing, then continue drilling or clean out a previously drilled hole, and subsequently install another section of uncemented casing below the first. However, the wellbore and each successive casing will have a smaller diameter. The ultimate production from and physical access to the well is accordingly limited in these prior art methods.